The present invention relates to air cycle systems and methods of reducing icing in air cycle systems for climate control of a vehicle cabin.
Air cycle systems are known and are used in some industries. An air cycle system may include an air compressor for receiving ambient air, an intercooler to receive compressed air from the compressor, and an expander in tandem to the air compressor for expanding the air.
In many air cycle systems, condensation is a concern. Manufacturers have been challenged in providing systems to efficiently handle condensation and icing when it occurs. For example, the humidity ratio at the inlet of the expander can be as high as 0.024 g/kg (water vapor/air). At the exit of the expander, the air can typically only hold a ratio of about 0.004 g/kg. The remainder of the water vapor condenses out, into liquid form. If however, the temperature exiting the expander is below freezing, the resulting condensate will turn to ice. Icing can cause problems relating to efficiency and plugging of the flow channels.
Thus, it is desired to further reduce or prevent icing from occurring in an air cycle system such as at the outlet of an expander.
The present invention generally provides systems and methods of preventing or reducing icing within an air cycle system in an automotive vehicle. In air cycle systems, icing at the expander outlet can occur if the expander inlet air pressure, expander inlet air temperature, and relative humidity of the air are within certain ranges. It has been found that icing can be prevented at the expander outlet by adjusting the temperature of air at the expander inlet, or by adjusting the air pressure ratio across the expander. This may be accomplished by increasing the temperature of air at the expander inlet, or by decreasing the pressure ratio across the expander.
The present invention includes an air cycle system having a preventative icing feature for climate control of a vehicle cabin. The air cycle system comprises a compressor for compressing air, an intercooler for cooling air from the compressor, an expander for expanding air to atmospheric pressure, and means for controlling the air temperature exiting the expander. The compressor has a compressor inlet for receiving ambient air and a compressor outlet for exiting compressed air. The intercooler has an intercooler inlet for receiving compressed air from the compressor and an intercooler outlet for exiting the cooled air. The expander has an expander inlet for receiving air from the intercooler and an expander outlet for exhausting the air to the passenger cabin.
In one embodiment, means for controlling the air exiting the expander includes a by-pass system for by-passing air around the intercooler to control the expander inlet air temperature. In another embodiment, means for controlling the air temperature exiting the expander includes a temperature control system having a variable speed fan cooperating with the intercooler to control the efficiency of the intercooler. In yet another embodiment, means for controlling the air temperature exiting the expander includes a pressure control system having a valve cooperating with the expander to control the pressure ratio across the expander.
Other objects and advantages of the present invention will become apparent upon considering the following detailed description and appended claims, and upon reference to the accompanying drawings.